I'm working on creating a to dimensional histogram that displays opening angle versus energy sum for each pair of clusters. For some unknown reason, the cosine of the opening angle is not at all bound by +1 -1. Something must be wrong with either the Dot product or magnitude calculations, but both of these are called from existing ROOT functions. 

     Again, the current code cam be found at /star/u/aschille/PhotonJetClusterMaker10.C.